@phdthesis{Wahl2019,
  author    = {Wahl, Joachim},
  title     = {The Use of Ionic Liquids in Capillary Electrophoresis Enantioseparation},
  doi       = {10.25972/OPUS-17639},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-176397},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2019},
  abstract  = {Two chiral chemical molecules being mirror images of each other, also referred to as enantiomers, may have different pharmacokinetic, pharmacodynamic, and toxicological effects. Thus, pharmaceutical manufacturers and authorities are increasingly interested in the approval of enantiopure drugs. However, the isomeric purity and the limits for isomeric impurities have to be specified applying enantioselective analytical methods, such as capillary electrophoresis. The separation of enantiomers in capillary electrophoresis may be improved by the addition of ionic liquids to the background electrolyte. The aim of this work was to investigate the influence of different separation conditions on the enantioseparation of phenethylamines in background electrolytes containing ionic liquids based on tetrabutylammonium cations. Best chiral separations were achieved at acidic pH values using phosphate buffers containing 125 mmol/L tetrabutylammonium based salts. Different reasons explaining enhanced enantioseparations in buffers containing ionic liquids were found. First, due to an improvement of the cyclodextrin solubility, the addition of ionic liquids to the background electrolyte enables the use of higher concentrations of these chiral selector. Furthermore, the adsorption of tetrabutylammonium cations to the negatively charged capillary surface results in a reduction of the electroosmotic flow. Hence, the resulting prolongation of migration times leads to a longer period of time for the separation of temporarily formed diastereomeric analyte cyclodextrin complexes, which yields improved enantioseparation. Additionally, due to a decrease of the adsorption of positively charged phenethylamine analyte molecules to capillary surface silanol groups, the adsorption of ionic liquid cations inhibits peak broadening. A further reason explaining an enhanced enantioseparation by the addition of ionic liquids to the background electrolyte is a competition between tetrabutylammonium cations and analyte enantiomers for the inclusion into cyclodextrin cavities. Furthermore, the influence of different chiral counterions, combined with tetrabutylammonium cations, on the enantioseparation of phenethylamines was investigated. Solely anions based on the basic proteinogenic amino acids L lysine and L arginine yielded chiral separation results superior to those achieved using achiral tetrabutylammonium chloride as background electrolyte additive. Especially the application of tetrabutylammonium L argininate gave very good enantioseparations of all investigated ephedrine derivatives, which might be explained by the ability of L arginine to affect the formation of complexes between analytes and cyclodextrins. Besides the investigation of the influence of ionic liquids on the enantioseparation, complexes between phenethylamine enantiomers and β cyclodextrin derivatives were characterized by affinity capillary electrophoresis. The binding constants between analyte enantiomers and cyclodextrins and the electrophoretic mobilities of the temporarily formed complexes were determined and compared to the observed chiral resolution values. While neither the calculated binding constants nor their differences correlated with the quality of the enantioseparation, a strong correlation between the differences of the electrophoretic mobilities of the complexes and the chiral resolution values was found.},
  subject      = {Kapillarelektrophorese},
  language  = {en}
}
@phdthesis{Hoerr2008,
  author    = {H{\"o}rr, Verena},
  title     = {Methoden zur Evaluation von Zytotoxizit{\"a}t und Struktur-Wirkungs-Beziehungen an Trypanosoma brucei brucei},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-27543},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2008},
  abstract  = {Im Rahmen dieser Arbeit wurden potenzielle Wirksubstanzen zur Behandlung trypanosomaler und bakterieller Infektionen gesucht. W{\"a}hrend auf dem Gebiet der Trypanosomiasis das Ziel in der Testung großer Substanzbibliotheken auf antitrypanosomale Wirkung und in der Erstellung von Struktur-Wirkungs-Beziehungen bestand, lag im Bereich der bakteriellen Infektion der Schwerpunkt in der Entwicklung neuer Testmethoden. Die Untersuchungen erfolgten mittels Kapillarelektrophorese und magnetischer Kernresonanz.},
  subject      = {Trypanosomiase},
  language  = {de}
}